1. Field of the Invention
The present invention relates to a fluid distributor, especially an air distributor which is particularly but not exclusively intended for use in conjunction with a so-called pressure wave mattress or other similar inflatable human body support, such as a cushion. Pressure wave mattresses and other such supports are used in the medical field to prevent bed sores. In this specification, for convenience we will use the term "mattress" for all such supports. The invention also relates to an assembly of a pressure wave mattress and an air distributor.
2. Description of the Prior Art
In our UK patents 1595417 and 2183471, we disclose pressure wave mattresses which are inflatable with air and air distributors for supplying and controlling the air input. The mattresses comprise arrays of air receivers, in the form of inflatable tubes, and in each case the air distributor directs the air to each array in sequence.
In GB-A-1595417 (U.S. Pat. No. 4,193,149), the air distributor comprises a chamber in which a rotor is mounted with one major surface in sealing contact with a cover plate or wall. Pressurized air is supplied to the chamber in a peripheral air inlet in the cover plate. Three circumferentially spaced air outlets lead from the cover plate, in the region thereof contacted by the rotor. Apertures are provided in the rotor at appropriate positions for cyclic alignment with the said outlets so that as the rotor turns air is cyclically fed to said outlets. The rotor is also provided with a recess in its surface contacting the cover plate, which is disposed so as to cyclically connect the said air outlets to a vacuum source, via a centrally located port in the cover plate. Consequently, during each revolution of the rotor, the respective outlets are sequentially supplied with air and then connected to vacuum for exhaustion.
To ensure that the air pressure in the rotor chamber does not reach excessive levels a pressure release valve is also provided. When the air pressure in the mattress falls below a certain level, for example in the event of a power failure, an alarm is sounded.
In GB-A-2l8347l (U.S. Pat. No. 4,711,275), the air distributor includes a solenoid valve which is used to prevent the air receivers from losing pressure, by closing the exhaust port for example in the event of an electrical power failure during normal operation. However, the solenoid valve cannot contain pressure loss resulting from a leak in the internal pipework of any compressor unit supplying air to the distributor whilst a normal voltage is still being applied to the apparatus.